Various deprecated code regarding EXT:form and FormEngine
have been removed.

* IRRE CustomControls without userFunc is not possible anymore.
* TBE_MODULES's configureModuleFunction is removed
* EXT:form type "GridContainer" is removed (use GridRow)
* EXT:form form configuration files must end with .form.yaml.
* EXT:form renderingOptions._isHiddenFormElement and
renderingOptions._isReadOnlyFormElement are removed
* CLI Command "lang:language:update" is now only
available under "language:update"